package com.cuit.qx.utils.tools;

import java.io.ByteArrayOutputStream;

/**
 * 用户密码加密功能公共类
 * @author fei
 *
 */
public class RSAUtils {
	private static byte[] base64DecodeChars = new byte[] { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
		-1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4,
		5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26,
		27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1,
		-1, -1, -1 };

public static byte[] decode(String str) {
	byte[] data = str.getBytes();
	int len = data.length;
	ByteArrayOutputStream buf = new ByteArrayOutputStream(len);
	int i = 0;
	int b1, b2, b3, b4;

	while (i < len) {
		do {
			b1 = base64DecodeChars[data[i++]];
		} while (i < len && b1 == -1);
		if (b1 == -1) {
			break;
		}
		do {
			b2 = base64DecodeChars[data[i++]];
		} while (i < len && b2 == -1);
		if (b2 == -1) {
			break;
		}
		buf.write((b1 << 2) | ((b2 & 0x30) >>> 4));

		do {
			b3 = data[i++];
			if (b3 == 61) {
				return buf.toByteArray();
			}
			b3 = base64DecodeChars[b3];
		} while (i < len && b3 == -1);
		if (b3 == -1) {
			break;
		}
		buf.write(((b2 & 0x0f) << 4) | ((b3 & 0x3c) >>> 2));

		do {
			b4 = data[i++];
			if (b4 == 61) {
				return buf.toByteArray();
			}
			b4 = base64DecodeChars[b4];
		} while (i < len && b4 == -1);
		if (b4 == -1) {
			break;
		}
		buf.write(((b3 & 0x03) << 6) | b4);
	}
	return buf.toByteArray();
}
}


